Air-permeable product and method of making it



Jan. 26, 1960 R. D. BRADLEY ETAL 2,922,417

1 AIR-PERMEABLE PRODUCT AND METHOD OF MAKING IT Filed June 11. 1953 2 Sheets-Sheet 1 TECH.

ATTORN Jan. 26, 1960 R. D. BRADLEY ETAI- 2,922,417

AIR-PERMEABLE PRODUCT AND METHOD OF MAKING IT Filed June 11, 1953 2 Sheets-Sheet 2' ATTORNEY:

AIR-PERMEABLE PRODUCT AND METHOD OF MAKING H Robert D. Bradley, Plainfield, N.J., and George M. Goettelman, Philadelphia, Pa, assignors to Johnson & .lohnson, a corporation of New Jersey Application June 11, 1953, Serial No. 360,913

15 Claims. (Cl. 128-141) This invention is directed to molding a bead or rim of plastic or rubber-like material to the edge of a sheet.

The techniques of the invention are advantageously applied to the manufacture of masks wherein it is desirable to form a leak-proof joint between sheet material and a plastic head or rim, and other articles in which -a flexible insert is contained in a plastic rim.

In the design and production of a mask to be used, e.g. in the operating room or as a gas mask, there are many factors which must be taken into consideration. Among the most important of these factors is the provision of the maximum possible area of filtering element so that pressure drop will be low, thereby facilitating breathing. The materials of construction must be low in cost with a minimum of non-essential parts in the mask. Further, for obvious reasons the mask must fit tightly against the face and head of the wearer.

In previously known types of masks, various complicated means have been provided to hold the filter securely against gas leakage, obtain a gas-tight connection around the head and face of the wearer, and provide a fabric gas-impermeable envelope connecting the filter element with the face-sealing element. These prior art masks are unsuitable where, as in the present case, it is desired to provide an economical mask, i.e., without the envelope portion, which may be manufactured by mass production.

According to the present invention, the foregoing requisites are fulfilled by providing a flexible insert having a plastic rim molded to its edge. In a specific embodiment of the invention, there is provided a mask having substantially the entire face portion made of flexible filtering material and having resilient plastic material molded and sealed to its edges forming face-contacting portions adapted to provide a substantially gas-tight seal against the face of the wearer. The need for the gasimpermeabie envelope in prior art masks, intermediate the filter and face-contacting rim, is thereby eliminated. Certain aspects of the invention are directed to improved techniques for molding plastic material to a flexible sheet, apart from manufacture of masks, as will appear hereinafter.

Using known procedures, it has not been possible to prepare an economical mask in which the filtering element also covers the face and is joined at its edge in leak-proof fashion to a resilient plastic or rubber-like head or rim. The reason for this disability in prior art procedures is that prior to the invention it has not been possible to injection mold a flexible sheet or insert directly to a plastic rim, as will appear more clearly from the ensuing presentation.

The invention and the manner in which the advantages accrue thereto as contrasted .with the enumerated disadvantages in prior art means and methods may be conveniently understood by reference to the attached drawings, considered together with the following description.

from the side opposite the face;

United States Patent Fig. 2 is a perspective view of the mask as it appears adjusted in position on the wearer;

Fig. 3 shows died out sections of paper or fabric adapted to be used as filtering elements for invention purposes;

Fig. 4 is a detailed section drawn to a larger scale of the filtering sheet material of the invention mask and showing how the various plies are disposed one against the other;

Fig. 5 illustrates one phase in the procedure for making the invention product;

Fig. 6 illustrates another phase in the manufacture of the invention product;

Fig. 7 drawn to a larger scale shows in greater detail a cross-section of the invention filtering element;

Fig. 8 illustrates again the filtering element of Fig. 7 after further processing operation has been performed thereon;

Fig. 9 illustrates a mold used in manufacturing the invention mask;

Fig. 10 shows a portion of the filtering sheet as it appears in the mold, the section being taken on a plane corresponding with plane 10 of Fig. 9;

Fig. 11 shows a cross-section of a portion of the mask to a larger scale taken along plane 1111 of Fig. 1;

Fig. 12 is similar to Fig. 5 but illustrates one phase in a modified procedure for making the invention product; and

Fig. 13 shows a cross-section of a portion of a modified type mask as seen in a relation similar to that of Fig.i 1L V The reference numbers indicate corresponding parts on the various figures. w

The mask is composed of a flexible fabric portion 20 and an edge portion 21 of flexible plastic injection molded thereto.- The composition of fabric ZO'Which accomplishes filtration, is illustrated in'Fig. 4. It is a laminate of fibrous layers, e.g. six layers of gauze 22 with adjoining layers of cellulose fibers 25 some of which are preferably impregnated with carbon black or other ad'- sorbent material.

The blank of this laminate of flexible material shown in Fig. 3 is first died out of a large flat sheet. A large number of these blanks are then stacked with their edges, in registration as shown in Fig. 6 and are sprayed only;

at their edges with an adhesive which, as will appear below, will serve as an important stiffening agent in subsequent processing. One then obtains a blank, the edge portions of which are shown in Fig. 7, having various laminae adhered together at the edge by the adhesive,- The edges of the blank, before or after the adhesive has' dried, are thenheat pressed together to confine them as of the sheet edge 37 area may be applied between pressing rings 32 disposed slightly inward from the extreme outward edge of the sheet and before the adhesive has dried as shown in Fig. 5. This causes the edges 37 to spread slightly, which renders them more receptive to plastic rim-forming material to be applied later. However, careis taken to avoid pressing the sheet so far inward from the sheet edge that the edges splay out perpendicular to the plane of the sheet thereby to project to or through the plastic rim. Such splaying or projection of sheetedges through the rim would materially and adversely affect the gas-tightness of the rim seal. It is a paramount.

object of the invention to prevent this adverse elfect 'According to a still further modification of the manner of pressing the adhesive-containing edge of the flexi ble'sheet, a pair of. pressing rings 32 of the type 'illus trated in Fig. 12 are employed. As the drawing illus trates, these rings have abutting faces 36, intermediately spaced faces 37' which grip the fabric and widely spaced faces 38 thereby defining a T-shaped cross-section when pressing rings 32 are in co-operating position. Faces 37 grip the fabric somewhat inwardly from the edge 37 in much the same way as pressing rings 32 described above in connection with Fig. 5, thereby to cause limited spreading of the extreme outward edges of the sheet in a direction perpendicular to the surface of the sheet and into more remote portions of the T-shaped zone. In the pressing operation excessive adhesive from the sheet edge also tends to be pressed outwardly into the T-shaped zone thereby substantially completely filling any void space therein. The combination of hardened adhesive and sheet edge fibers thereby assumes the shape similar to this zone. 7

The heat pressing hardens the adhesive, in instances Where the adhesive was not hard before such pressing; after pressing, the blank of flexible material, having the hardened edge, is ready to be placed in the injection mold illustrated in Fig. 9. The edge portions 26 of the blank as seen in Fig. 10 are squeezed between land areas 30 and 31 of the mold. The molten plastic is then introduced into mold cavity 33. After the plastic has become set the mold is opened. The blank, now having bead or rim 35 of flexible plastic adhered thereto is removed from the mold.

- The internal structure of the joint between the plastic rim 21 and the flexible insert 20 is clearly shown in Figs. 11 and 13. It is seen that the insert edges 37 remain substantially as they were after heat pressing as shown in Figs. 5, 8 and 12. Fig. 13 illustrates an improved type of anchoring obtained through use of controlled spreading of the sheet edges produced by the technique described above in connection with Figs. and 12. In each case there is no splaying of the edges through the surfaces of head 35 which would detract from the gastightness of the insert-rim bond. One notable advantage of the present invention is that hardening of these edges is effected by the procedure described herein so that this splaying is eliminated or at least reduced to the point where the sheet edges do not protrude through the external surface of head 35.

After removing the injection molded structure from the mold the bottom portions and 11 of the fiat piece as shown in Fig. l are pressed together and sealed with heat to form a chin section 12. Chin section 12. preferably is so formed as to fit snugly against the chin of the wearer thereby to prevent leakage of air around the chin when the mask is in position. Harness 16 is secured to tabs 17 of the mask and fits around the back of the head of the wearer to hold the mask snugly against the forehead, sides of the head and under the chin.

The mold, Fig. 9, is formed from an upper section 40 and a lower section 42. The face-contacting edge portion 21 of the mask is formed by depression 45 of the lower section of the mold. The plastic bead or rim which serves as a support for the flexible insert is formed by depression 46 in the lower part of the mold. Land areas 30 and 31 on the lower and upper sections of the mold, respectively, serve to compress the flexible insert and prevent flashing, i.e. flow of molten plastic into the zone of the flexible insert where it is undesired. The eye rims are formed by depression 50 in mold section 42. Raised portions 51 in lower mold section 42 come into direct contact with corresponding upper areas in mold section 40 to form the eye hole. Gates adapted to provide for inflow of molten plastic to the mold are shown at 55. Vents adapted to provide for escape of the trapped air during the flow of the molten plastic to the mold are provided at 60. Guide pins 61 in the top section 40 and corresponding guide recesses 62 in the bottorn section 42 assure proper registry of the two sections of the mold during use. Pipes and tubes 65 are provided for circulation of water or oil for heating the mold to proper temperature for operation. Clasps 70 retain mold portions 40 and 42 in juxtaposition during use.

The depth of vent 60 in lower section 42 may suitably be about 0.002 inch which is sufficient to permit escape of air while still preventing flow of plastic. The depth of area 45 may be 0.050 inch, while recess 46 which forms the bead securing the edges of the flexible insert may be 0.250 inch deep and 0.212 inch wide. The space between land areas of upper section 40 and lower section 4-2 when the mold is closed is about 0.030 to 0.040 inch; and the width of the land area is 0.100 inch.

The adhesive employed to secure together the layers of edge portion 37 and thereby stiffen said edge may be any material which has the property of binding together fibers of the sheet while still being reasonably compatible with the head or rim-forming plastic 35. The bonding agent is preferably heat-sensitive, i.e. softens with heat. An example of a satisfactory adhesive is a vinyl chloride copolymer emulsion internally plasticized by copolymerization. On drying, these products generally yield clear, glossy, flexible and extensible films. Suitable ma terial in this respect is identified by the trade name Polyco 446 manufactured and sold by American Polymer Corporation. The emulsion has a solids content of about 45% minimum, a pH of 3 to 5, and viscosity of 10 to 20 centipoises. Starch solution may also be used as an adhesive stiffening agent provided the amount present is maintained small enough so as to avoid undue incompatibility with the plastic rim-forming material. The bonding agent may be applied to the sheet edges by brush coating or methods other than the stacking and spraying technique specifically described above.

An outstanding advantage of the invention is that it provides a method and article in which a flexible sheet material has a plastic rim injection molded thereto. A variety of plastic materials may be used for the injection molding. One suitable material manufactured by a large plastic manufacturer is composed of 96 to 97% vinyl chloride copolymerized with 3 to 4% vinyl acetate. The copolymer is plasticized with dioctylphthalate and mixed with small amounts of filler, lubricant and stabilizer to provide a final composition having a durometer hardness reading of fifty plus or minus five. This mixture is first heated to melting and then forced into the mold during the injection molding operation according to usual technique. Due to the high pressure involved and the necessity of squeezing the edge portions of the flexible sheet between land areas as described above, which results in splaying of the laminae edges, certain advantages of the invention become particularly apparent when injection molding is used to aflix the plastic edge to the flexible sheet. However, the invention is not limited to injection molding plastics. If desired, plastisols, i.e. resins, suspended in plasticizer to make them fluid, may be used instead of the injection molded plastic, and heated to about C. to fuse the resin irreversably and thereby make a solid rim. In certain cases use of hard, i.e. non-elastomeric, plastic may be found advantageous. Still other procedures and techniques will be apparent to those skilled in the art. It will also be appreciated that the teaching of the invention may be used wherever it is desired to obtain a gas-tight contact between a flexible sheet and a plastic rim, and is not limited to manufacture of face masks.

We claim:

1. The method of molding a plastic rim to the edge portion of a flexible sheet of laminated fibrous fabric layers, which comprises stiffening the edge portion of said sheet with and adhesive without stiffening the center of said sheet whereby it remains flexible, the amount of said adhesive and the disposition thereof being such that,

when an area of said sheet adjacent but disposed in-..

wardly from said edge portion and outwardly from said center is compressed, splaying of said edge portion to the extent that the edge portion will reach the surface of the rim subsequently to be formed is prevented, compressing said sheet in said area in a molding machine to prevent substantial flashing of fluid plastic material through said area toward the center of said sheet when the plastic material is applied to said edge portion during molding, and molding said plastic material to said edge portion so as to enclose completely said edge portion, thereby to form said rim free of protruding sheet edges at its surface while said center remains flexible.

2. The method of molding an elastomeric plastic rim to a flexible sheet of laminated fibrous fabric layers, which comprises spraying the edge portion of said sheet with an adhesive stiffening agent without stiffening the center of said sheet whereby it remains flexible, the amount of said adhesive and the disposition thereof being such that, when an area of said sheet adjacent but disposed inwardly from said edge portion and outwardly from said center is compressed, splaying of said edge portion to the extent that the edge portion will reach the surface of the rim subsequently to be formed is prevented, compressing said sheet in said area between lands in a molding machine to prevent substantial flashing of fluid elastomeric plastic material through said area toward the center of said sheet when the plastic material is applied to said edge portion during molding, v

and molding said plastic material to said edge portion so as to enclose completely said edge portion, thereby to form said rim free of protruding sheet edges at its surface while saidcenter remains flexible.

3. The method of molding an elastomeric plastic rim to the edge portion of a flexible sheet of laminated fibrous fabric layers containing heat-sensitive adhesive stiffening agent, which comprises pressing and heating the edge portion of said sheet so that when an area of said sheet adjacent'but disposed inwardly from said edge portion and outwardly from said center is thereafter compressed, splaying of said edge portion to the extent that the edge portion will reach the surface of the rim subsequently to be formed is prevented, compressing said sheet in said area in a molding machine to prevent substantial flashing of fluid plastic material through said area toward the center of said sheet when the plastic material is applied to said edge portion during molding, and molding said elastomeric plastic material to said edge portion so as to enclose completely said edge portion, thereby to form said rim free of protruding sheet edges at its surface while said center remains flexible.

4. The method of molding an elastomeric plastic rim to the edge portion of a flexible sheet of laminated fibrous fabric layers, which comprises stiffening the edge portion of said sheet with an adhesive compatible with said elastomeric plastic without stiffening the center of said sheet whereby it remains flexible, the amount of said adhesive and the disposition thereof being such that, when an area of said sheet adjacent but disposed inwardly from said edge portion and outwardly from said center is compressed, splaying of said edge portion to the extent that the edge portion will reach the surface of the rim subsequently to be formed is prevented, compressing said sheet in said area between lands in a molding machine to prevent substantial flashing of fluid plastic material through said area toward the center of said sheet when the plastic material is applied to said edge portion during molding, molding under pressure heated fluid elastomeric plastic material to said edge portion so as to enclose completely said edge portion, and cooling said plastic thereby to form said rim free of protruding sheet edges at its surface while said center remains flexible.

5. The method of molding an elastomeric plastic rim to the edge portion of a flexible sheet of laminated fibrous fabric layers which comprises wetting the edge portion of said sheet with a heat-sensitive adhesive stiffening agent without stifiening the center of said sheet whereby it remains flexible, pressing and heating the edge portion of said sheet to dry said adhesive so that when an area of said sheet adjacent but disposed inwardly from said edge portion and outwardly from said center is thereafter compressed, splaying of said edge portion to the extent that the edge portion will reach the surface of the rim subsequently to be formed is prevented, compressing said sheet in said area in a molding machine to prevent substantial flashing of fluid plastic material through said area toward the center of said sheet when the plastic material is applied to said edge portion during molding, and molding said elastomeric plastic material to said edge portion so as to enclose completely said edge portion, thereby to form said rim free of protruding sheet edges at its surface while said center remains flexible.

6. The method of molding an elastomeric plastic rim to the edge portion of a flexible sheet of laminated fibrous fabric layers which comprises wetting the edge portion of said sheet with a heat-sensitive adhesive stiffening agent without stiffening the center of said sheet whereby it remains flexible, heating said moistened portion of said sheet and pressing said edge portion inwardly from the extreme edge and outwardly from said center thereby to cause spreading of said extreme edges and hardening of said adhesive with the edges in said spread condition, the amount of said spreading being such that when an area of said sheet adjacent but disposed inwardly from said edge portion and outwardly from said center is thereafter compressed, splaying of said edge portion to the extent that the edge portion will reach the surface.

of the rimsubsequently to be formed is prevented, compressing said sheet in said inward area in a molding machine to prevent substantial flashing of fluid plastic material through said area toward the center of said sheet when the plastic material is applied to said edge portion during molding, and molding said elastomeric plastic material to said edge portion so as to enclose completely said edge portion, thereby to form said rim free of protruding sheet edges at its surface while said center remains flexible.

7. The method of making a gas mask which comprises cutting a blank from a flat sheet of fibrous air-permeable, flexible laminated layered fabric filtering material, said blank having a circumferential edge portion and eye apertures with edge portions, stiffening said circumferential edge portion and the edge portions of said eye apertures with an adhesive compatible with elastomeric plastic material subsequently to be used without stiffening the center of said sheet whereby it remains airpermeable and flexible, the amount of said adhesive and the disposition thereof being such that, when an area of said sheet adjacent but disposed inwardly from said edge portions and outwardly from said center is compressed, splaying of said edge portion to the extent that the edge portion will reach the surface of the rim subsequently to be formed is prevented, compressing said sheet between lands in a molding machine in said inward areas co-extensive with said edge portions to prevent substantial flashing of fluid elastomeric plastic material through said area toward the center of said sheet when the plastic material is applied to said edge portions during molding, molding under pressure heated fluid elastomeric plastic material to said edge portions so as to enclose completely said edge portions and cooling said plastic, thereby to form a rim surface free of protruding fibers caused by splaying of said sheet edge while said center remains air-permeable and flexible.

8. In the method of making a mask from a flat sheet of fibrous air-permeable, flexible laminated layered fabric filtering material having edge portions, the improvement which comprises wetting said edge portions with a heatsensitive adhesive stiffening agent without stiffening the center of said sheet whereby it remains air-permeable and flexible, heating said moistened portions of said sheet and pressing said edge portions inwardly from the extreme edges and outwardly from said center thereby to cause spreading of said extreme edges and hardening of said adhesive with the edge portions in said spread condition, the amount of said spreading being such that when an area of said sheet adjacent but disposed inwardly from said edge portions and outwardly from said center is thereafter compressed, splaying of said edge portions to the extent that the edge portions will reach the surface of the rim subsequently to be formed is prevented, compressing said sheet in said inward area in a molding machine to prevent substantial flashing'of fluid plastic material through said area toward the center of said sheet when the plastic material is applied to said edge portions during molding, and molding said elastomeric plastic material to said edge portions so as to completely enclose said edge portions, thereby to formsaid rim free of protrudingsheet edges at its surface while said center remains air-permeable and flexible.

9. The method of making a gas mask which comprises cutting a blank from a flat sheet of fibrous air-permeable, flexible laminated layered fabric filtering material, said blank having edge portions, spraying said edge portions with an adhesive stiffening agent compatible with elastomeric plastic material subsequently to be used without stiffening the center of said sheet whereby it remains air-permeable and flexible, the amonnt of said adhesive and the disposition thereof being such that, when an area of said sheet adjacent but disposed inwardly from said edge portions and outwardly from said center is compressed, splaying of said edge portions to the extent that the edge portions will reach the surface of the rim subsequently to be formed is prevented, compressing said sheet between lands in a molding machine in said inward areas co-extensive with said edge portions to prevent substantial flashing of fluid 'elastomeric plastic 'material through said area toward the center of said sheet when the plastic material is applied to said edge portions during molding, molding under pressure heated fluid elastomeric plastic material to said edge portions so as to enclose completely said edge portions and cooling said plastic, thereby to form a rim surface free of protruding fibers caused by splaying of said .sheet edge while said center remains air-permeable and flexible.

10. An article of manufacture comprising a flexible, air-permeable, fibrous sheet material including an inner portion and an edge portion; an adhesive stiffening agent in said edge portion but not extending to said inner portion whereby said edge portion is stiffened by the application of said stiffening agent and said inner portion remains flexible and air-permeable; and a plastic rim molded to said edge portion and compatible with said adhesive thereon.

11. An article of manufacture comprising a flexible, air-permeable, fibrous sheet material including an inner portion and an edge portion; an adhesive stifiening agent in said edge portion but not extending to said inner portion whereby said edge portion is stiffened and said inner portion remains flexible and air-permeable; and a heatsensitive, heat-softenable plastic rim molded to said edge portion and compatible with said adhesive thereon, said rim being free of protruding fibers caused by splaying of said sheet edge,

V 8 12..An article of manufacture comprising a flexible, air-permeable sheet material of laminated fibrous fabric layers including an inner portion and an edge portion; an adhesive stiffening agent in said edge portion but not extending to said inner portion whereby said edge portion is stiffened and said inner portion remains flexible and air-permeable; and a plastic rim molded to said edge portion and compatible with said adhesive thereon.

13. A gas mask comprising a flexible, air-permeable, fibrous face-piece including an inner portion and an edge portionyan absorbent material impregnating'said facepiece and acting as a filter to prevent undesirable materials from passing therethrou'gh; an adhesive stiffening agent in said edge portion'but not extending to said inner portion whereby said edge portion is stiflened and said inner portion remains flexible and air-permeable; and a plastic face-contacting rim molded to said edge portion and compatible with said adhesive thereon.

14. A gas mask comprising a flexible, air-permeable fibrous face-piece including an inner portion and an edge portion; an absorbent material impregnating said facepiece and acting as a filter to prevent undesirable rnaterials from passing therethrough; an adhesive stiffening agent in said edge portion "but not extending to said inner portion whereby said edge portion is stiffened and said inner portion remains flexible and air-permeable, and a heat-sensitive, heat-softenable plastic rim molded to said edge portion and compatible with said adhesive thereon, said rim being free of protruding fibers caused by. splaying of said edge portion.

15. A gas mask comprising aflexible, air-permeable face-piece of laminated fibrous fabric layers including an inner portion and an edge portion; anabsorbent material impregnating said face-piece and acting as a filter to prevent undesirable materials from passing therethrough; an adhesive stifiening agent in said edge portion but not extending to said inner portion whereby said edge portion is stifiened and said inner portion remains flexible and air-permeable; and a plastic face-contacting rim molded to said edge portion and compatible with said adhesive thereon.

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